It is commonplace in the recreational vehicle business to use composite sheets, such as glass fiber-reinforced wall panels, for the exterior surface of a recreational vehicle. These wall panels vary in widths up to, and including, dimensions from 2.4 to 3 meters (8 to 10 feet), and can have a length as long as 12 meters (40 ft.) or more. While the composite material from which the panels are made provides an adequate material for the recreational vehicle side walls, it would be advantageous to provide an improved composite sheet having a stronger bond between respective layers of the composite sheet.